1. Technical Field
The present invention relates to a wireless type communication terminal and a mobile type wireless communication terminal, and is particularly applicable to a clamshell type mobile telephone and the like.
2. Related Art
In recent years, there have been attempts to increase the resolution of liquid crystal displays in the mobile telephones so that still pictures or moving images taken by the digital cameras can be displayed with higher definition in addition to normal still images such as characters and graphics. This increases data quantities exchanged between a digital camera and a liquid crystal display and the use of LVDS (Low Voltage Differential Signaling), a high speed transfer system for connection with a display part or an image sensing device has been proposed.
Recent mobile telephone handsets mostly employ the clamshell design because its foldable structure allows the mobile telephones to have a larger display size while their portability is not impaired and the design can prevent operation buttons from being accidentally pressed while the users carry the handsets around. The clamshell design has a first case member including a control portion that mainly controls the external wireless communication function of the mobile telephone and a second case member having a display part. The first and second case members are hinged together and can be opened and closed through the hinge.
However, as the resolution of the display part placed in the mobile telephone increases, the number of pins in a flexible wiring board used for sending signals to the display part must be increased to transmit high bit rate image data or the like to the display part through a wire. Therefore, in a mobile telephone handset with a clamshell design, the flexible wiring board with an increased number of pins must be passed through the hinge to allow the data transmission between the first and second case members through a wire, which complicates the hinge structure or the packaging process. This is not only an obstacle to reduce the size of the mobile telephone handset, but also pushes up the cost, and the reliability can be lowered.
Meanwhile, instead of the flexible wiring board, an internal wireless communication antenna may be provided in each of the first and second case members, so that data transmission between the first and second case members can be carried out by internal wireless communication. In this case, the communication suffers from interference with wireless communication outside the mobile telephone. Therefore, the environment for the internal wireless communication changes depending on the wireless communication outside the mobile telephone, and the reliability in surely transmitting data can be deteriorated.
When a wireless communication method operating with low limited output by UWB (Ultra Wide Band) is employed for the internal wireless communication in particular, the power level is greatly different from the waves output by the wireless communication outside the mobile telephone, and the power level difference could be as large as 90 dB.
Therefore, the effect of even a signal outside the band of interest upon the internal wireless communication could not be ignored, the interference with the wireless communication outside the mobile telephone degrades the wireless communication environment, the bit error rate increases and retransmission caused by increase in the packet error rate could be increased.
According to a method disclosed by Japanese Patent Publication No. 2003-507954, a branch unit to branch a part of a transmission signal in a stage before the antenna is provided so that a very weak GPS signal can be received while transmission is carried out by the mobile communication. A branch signal from the branch unit is attenuated or phase-shifted to produce an interference compensation signal, and the interference compensation signal is superposed on the GPS signal.
According to the method disclosed by Japanese Patent Publication No. 2003-507954, the branch unit, an attenuator, a phase shifter and a superposing unit are necessary. A complicated and large-scale circuit configuration is necessary, and the cost, size, and weight are increased.